As a process for producing epoxy compounds from olefins, oxygen and hydrogen, for example, a process using a noble metal compound and titanosilicate is known. As a process for producing propylene oxide using a catalyst containing TS-1 and Pd, there are reported a process for producing propylene oxide which comprises reacting hydrogen/oxygen/propylene in the presence of a catalyst of Pd and Au supported on TS-1, wherein water is used as a solvent and hydroquinone is added thereto (see Heisei 12 nendo Jisedai Kagaku Process Gijutu Kaihatu Non-halogen Kagaku Process Gijutu Kaihatu Seika Houkokusho (Report of R&D projects for Technology of Next-generation Chemical Process/Technology for Non-halogen Chemical Process” FY2001 Annual Report), pp. 249-258 (2002)).